I'll be going cage diving in a couple of months in South Africa with great white sharks (hopefully they will show up to this meeting ), and am wondering if I should get a ziploc-style waterproof bag for my D300+sb600 or if I should rather get a small waterproof P&S?

I have never taken any photos underwater or with an underwater casing, so I have very little idea about their limitations.

not sure what you mean by a ziplock style bag but if you do go this route make sure to get a good one as the last thing you want is for it to leak. Also... make sure the piece which protects the lens is optically correct to the amount it can be. If you dont have this you may as well get yourself a P&S and take that. A good cover isnt cheap either.

I guess the question becomes how much underwater photography are you going to be doing? If it will be few and far between I would opt for a P&S or a decent cover which isnt too expensive. If you plan on doing it often go for a good one but they can be very expensive.

One other thing.. when you come out of the water rinse the bag with fresh water before taking out the camera. You dont want to take the chance of having salt water get on the camera if you dont have to. I dont worry so much about the body but I do worry about the lens and/or filter. When I was taking pics of whales this spring my lens got splashed by a sea lion. I dried it off and later seen some very small scratches... This was due to the water evaporating and the dry salt that remained scratching the filter a bit... not bad and I couldnt see it on any pics but doing this repeatedly would not be wise. Same thing applies for the piece of plastic which covers the lens and is another reason you want to rinse it with fresh water.

I was referring to Ewa Marine's Underwater Housings. B&H have them, I'm just not sure about the policy here regarding links.

I don't plan on doing too much UW photography in the near future, but really want to get decent photos on my cages diving trip. I can't afford several thousand Dollars for a solid UW housing and the additional gear, but I guess I am willing to spend the $250-$300 on one of these UW housings if my equipment will be able to perform adequetely underwater in those conditions.

By the way, do you think I would get more responses in a different forum?

I know of several ppl who have used this brand and they love it... I wouldn't take it to any dpeth though but you wont have to worry about that in a shark cage...

Give it a good test at home by just filling it with air and placing it underwater to check for leaks... get really familiar with the sealing mechanism to ensure it is sealed properly before you take it underwater. With a soft plastic case like this check out the shark cage good before hand and look for places where it may get snagged up and potentially rip the housing... depending on the cage sometimes the bolts used to assemble it can catch objects and in this case rip the plastic. You're gonna be temped to stick the camera through the opening for a clean shot.. dont do it with a soft plastic housing... or any housing for that matter A friend of mine lost a great camera that way... took a few minutes for the shark ot realise it wasnt shark food.

If you buy this unit... when you are getting ready to enter the cage... ductape the seal as an added precaution from being opened by accident.